Diffuse t(1) reduction in gray matter of sickle cell disease patients: Evidence of selective vulnerability to damage?

The objective of our study was to test the hypothesis that subtle brain abn ormality can be present in pediatric sickle cell disease (SCD) patients nor mal by conventional MR imaging (cMRI), We examined 50 SCD patients to ident ify those patients who were normal by cMRI, Quantitative MR imaging (qMRI) was then used to map spin-lattice relaxation time (T-1) in a single slice i n brain tissue of all 50 patients and in 52 healthy age-similar controls. W e also used a radiofrequency (RF) pulse to saturate blood spins flowing int o the T-1 map slice, to characterize the effect of blood how on brain T-1. Abnormalities were noted by cMRI in 42% (21/50) of patients, with lacunae i n 32%, and encephalo malacia in 20%, Brain T-1 in patients normal by cMRI w as significantly lower than controls, in caudate, thalamus, and cortex (p l ess than or equal to 0.007), and regression showed that gray matter T-1 abn ormality was present in caudate and cortex by age 4 (p less than or equal t o 0.002), In patients abnormal by cMRI, T-1 reductions in gray matter were larger and more significant. White matter T-1 was not significantly increas ed except in patients abnormal by cMRI, RF saturation in a slab below the T -1 map produced no significant change in T-1, compared to RF saturation in a slab above the T-1 map, suggesting that inflow of untipped spins in blood does not cause an artifactual shortening of T-1, Gray matter T-1 abnormali ty was present in patients normal by cMRI, while white matter T-1 abnormali ty was present only in patients also abnormal by cMRI, These findings sugge st that gray matter is selectively vulnerable to damage in pediatric SCD pa tients and that white matter damage occurs later in the disease process. Ou r inability to find an effect from saturation of inflowing blood implies th at rapid perfusion cannot account for T-1 reduction in gray matter. (C) 199 9 Elsevier Science Inc.